Some lustrous members of the silica family. Jet and amber. The lapidary’s art.
Let us make it clear at the outset that the beaches of the British Isles yield no truly precious stones. If they did they would have been invaded long ago by hordes of treasure-seekers and our tranquil coast would have witnessed such uproarious scenes as are associated with a Klondyke gold rush. Some very impure and, therefore, almost valueless, sapphires can be found on the Island of Mull, and crystals of topaz were found long ago in Arran, Aberdeenshire and Argyll, but we must remain content with the study of stones that are designated semi-precious. Even they might be more appropriately styled demi-semi-precious.
Nearly all of them consist of silica in one form or another. By far the greater part of the earth’s crust consists of silica. We have encountered it already in enormous quantities in the multitude of flint pebbles, in the sandstone, quartz and quartzite pebbles, and in all of those that were formed from igneous rocks. You may think it strange that semi-precious stones consist of such common stuff. The reason is that the silica in these stones has undergone a very slight chemical change that has given them a brilliance and a colouring so different from silica in its cruder state as to trans- form them. Furthermore, silica possesses some of the virtues that characterize all gems: beauty, durability, hardness and rarity. Clearly, it can claim the second and the third, even in the form of the poor, common flint; the pebbles that we are about to describe can boast of the first; as to the fourth a less substantial claim can be made, but, in searching for semi-precious pebbles among beds of shingle, you may soon convince yourself that they are at least comparatively rare.
As most of the pebbles we shall look at in this article are varieties of quartz we can most conveniently consider quartz first and then inspect some of its very pleasing varieties. You already know that quartz is sihca itself. It abounds in the sand-grains of every sea-shore and desert and it has obtruded itself into most of the rocks in the earth’s surface. We find it in the form of veins in innumerable pebbles, including those of some sedimentary rocks. But, nearly always, it is the white, opaque quartz that is so abundant. The completely transparent, glassy quartz is much rarer. In that form it is commonly known as ‘rock-crystal’ and often as just ‘crystal’, a name which originated from the notion that it was petrified ice (Greek: Krustallos = ice). Marbodus, who was Bishop of Rennes in France in the eleventh century, wrote a Latin poem on gems. Here is a translated extract from his description of transparent quartz, which he calls ‘crystal’:
Crystal is ice through countless ages grown (So teach the wise) to hard transparent stone: And still the gem retains its native force, And holds the cold and colour of its source. Yet some deny, and tell of crystal found Where never icy winter froze the ground.
Some confusion exists even to-day in the minds of some pebble-collectors over the clear and the opaque kinds of quartz. They persist in calling the former ‘crystal’ and the latter ‘quartz’, whereas, of course, both are quartz.
Do not expect to find large pebbles of entirely pure, transparent quartz on the beach. They are usually small and are likely to have a frosted appearance, so that scraping, and, perhaps, breaking, will be necessary to secure identification. To find the really flawless specimens you will have to travel to Brazil. The perfect quartz crystal takes the form of a six-sided (hexagonal) prism with a six-sided pyramid at each end. The shape varies and the hexagon is sometimes irregular.
Waste no time in looking for such a prize. You must be content with small, fragmental pieces. Remember the hardness test and so make sure that you are not carrying home a piece of bottle-glass.
Now let us look at some of the varieties or relatives of quartz. Together they make up a most attractive family.
Amethyst, or amethystine quartz, is the transparent rock-crystal quartz with a fight purple or violet colour, due probably to the presence in the stone of some of the element, manganese. A cut and polished pebble of amethyst is a joy to behold and to possess. Good specimens were valuable about 150 years ago, but the price fell heavily when Germany imported large quantities of them into this country. Careful search can occasionally reveal the pebbles on some of the Cornish beaches. They also appear on the east coast of Scotland, whence some of them are carried by longshore drifting to the beaches of the north-east coast of England.
Rose Quartz, unlike amethyst, is not a variety of the transparent, but of the common opaque quartz. Even so, it is a very attractive pink stone and the pebbles are worthy of their place in a collector’s cabinet. Just as opaque quartz is much commoner than the clear rock crystal, so rose quartz is less rare than amethyst. The pink colouring is attributed to the presence of the metal titanium.
Citrine, or yellow quartz, is, like amethyst, a variety of the clear rock-crystal quartz. The colour varies from lemon-yellow to golden. This gives the stone some resemblance to the gem, topaz, and it is often sold under the label of Scotch topaz, occidental topaz or fake topaz, thereby fetching a higher price than yellow quartz could command.
Smoky Quartz, or Cairngorm, called after the Cairngorm Mountains in Scotland, from the massive granite of which they were extracted, is another, and very attractive, variety of rock-crystal quartz. Its colour ranges from yellow through deep orange to dark brown and it is accompanied by a smokiness that seems to lend added beauty to the lustre of the cut and polished pebble. The stones are familiar to all as the ornaments of Highland dress. The pebbles find their way to Scottish beaches and reach the east coast of England in course of time by longshore drifting. A good specimen is a joy to the lapidary. The more yellow kind, like citrine, is not unlike topaz, but it lacks the hardness and the heaviness of that gem.
Chalcedony (pronounced ‘Kal-sed-onni’, with the stress on the second syllable) takes its name from Chalcedon in Asia Minor. It is non-crystalline, translucent quartz with a milky blue-grey or pale brown tinge and a waxiness of lustre, but its chief characteristic is its extraordinary form. Its surface is raised in rounded lumps suggestive of a bunch of grapes or a collection of soap-bubbles, an arrangement technically known as concretionary or botryoidal (Greek: botrus = a bunch of grapes). When broken, chalcedony is seen to be of a fibrous structure. Extremely thin fibres that look like hairs radiate out from the centre of each rounded lump to its surface.
The ancient Babylonians, Persians, Etruscans, Greeks and Romans made much use of the stone for sculpture and ornamentation and it was in much demand for signet-rings. These had the reputation of bringing to their wearers good luck in their iitiga- tion. The poem from which we have already quoted says of chalcedony: But pierced and worn upon the neck or hand A sure success in lawsuits ‘twill command.
Yet, so slight is the difference in composition between chalcedony and the poor, common flint, that the latter may be said to be just an inferior form of it. It would be equally true to say that the other varieties of silica that we are about to examine differ only in very slight degree from chalcedony.
You must not expect to find good specimens of it without prolonged search, for it is considerably rarer than quartz. It originates from cavities in granite and other igneous rocks and sometimes in the Old Red Sandstones. Good specimens are found on the Scottish coast and on the eastern and southern coasts of England.
The remaining varieties of quartz that we shall look at resemble chalcedony so much in all but colour and surface-form that they might well be, and often are, called varieties of chalcedony. They are Agate, Onyx, Carnelian and Sard. All, like chalcedony, are non-crystalline and translucent forms of quartz. The cut and polished pebbles are charming, but you should take only your best specimens to the lapidary, as they are all harder than the most highly tempered steel and put up a stiff resistance to his cutting apparatus.
Of the several kinds of Agate (Latin: Achates = a river in Sicily) we can give our attention to the three that are the choicest and most striking.
Banded or striped agate is so called because its cut surface exhibits a succession of curved bands, stripes or layers, each band differing in colour from its neighbours. The curves are very roughly concentric and all of them are parallel to one another.
Agates came into existence in the cavities of igneous rocks in much the same way as flint is usually formed in the hollows of chalk —that is, by the solidifying of liquid silica in the cavities. But in the case of agate, the solution of silica did not fill the cavity and then solidify. There appear to have been several stages in the process, separated by some intervals of time. It is this that accounts for the difference in colouring of the layers. The first solution that poured into the cavity may have been pure silica, which solidified into colourless quartz, and the second may have contained a chemical which coloured it, and so on. The effect of this process is most charmingly revealed on the cut and polished surface of a banded agate pebble.
Sometimes the concentric banding takes the shape of the ground-plan of a fortress, the bands being more angular than curved and suggesting the bastions and salients in the fortress wall. A stone with banding of such a pattern is aptly called Fortification Agate. You will also observe that the banding is roughly parallel to the outer surface of the pebble and must consequently have been parallel to the walls of the cavity filled by the stone. This is not always so. It happens to be so in this particular pebble because it had had few of its corners rubbed off. Many agate pebbles have been so rounded that the banding has disappeared here and there from the surface.
Our third kind is Moss Agate. It contains no moss at all or, indeed, any other vegetable matter. The mossy-looking filaments that give it its name result from the infiltration of some inorganic material, possibly oxide of manganese. Their ramifications through the translucent silica, in which they seem to float, give the stone an enchanting appearance and make it the acknowledged favourite of many collectors.
Banded agates, though not common, are present in sufficient numbers on many of our beaches to reward a patient but not arduous search. Perhaps their highest frequency is on some parts of the Scottish coast, where agates sof alternating pink and white bands have long been known as ‘Scotch pebbles’. On the east coast of England there are good specimens at Scarborough, Filey, Cromer, Aldeburgh, Felixstowe, Ramsgate and Deal. Many beaches on the south coast are also productive, but the best of the hunting-grounds between Dover and Land’s End is the Cornish coast. The biggest and best agates come from other parts of the world. They abound so much in Brazil and Uruguay that it used to be customary to load them into ships as ballast and to transport them from those countries to Germany to be cut and polished. That process went on in and around a town called Oberstein, where a huge trade in agate-working had been established, the grinding mills being driven by bountiful water-power. Magnificent slabs of agate are cut and polished there for export throughout the world and for conversion into ornaments of every description. Commercial agate, however, must not be accepted at face value. The dull banding of some of the stones is artificially brightened by heating, staining and treatment with acids. The secrets of the agate-staining racket were known many centuries ago to Italian jewellers. In the last century they were passed on to the agate-workers of Oberstein and the practice still continues.
You will find far more joy in the small and modest agate pebble you have found on one of the home beaches, cut and polished by a local lapidary, than in any of the huge, coruscating, multicoloured slabs from Oberstein.
Onyx, an equally lovely stone, we can dismiss in a few lines. Imagine a banded agate in which the bands are straight, not curved: that is onyx. The stone lends itself admirably to the cutting of cameos. It is much rarer than banded agate and is consequently more valuable. The cameo-worker prefers the onyx of alternating black and white bands so that the figure he cuts on the white band can stand out against the background of black. You will be fortunate indeed to find an onyx pebble of clearly defined banding. You are more likely to discover a cloudy specimen with its black shading off into white through gradations of grey. This is a much less attractive stone than the commoner banded agate.
Be on your guard against the assumption that any pebble that contains straight bands must be an onyx. Innumerable pebbles of the commoner kinds contain straight bands of quartz. Slate and schist often have such banding. If you are in any doubt, apply the simple knife-blade test to the parts of the pebble that lie between the white bands. The blade will easily scratch the slate or schist pebble. It will make no impression upon any part of one that is onyx or agate.
Carnelian, formerly called Cornelian (Latin: cornu = horn) on account of its horny appearance, underwent a change of name in comparatively recent times, perhaps because carnelian, supposedly derived from the Latin, carneus = flesh-coloured, is more truly descriptive of it. It is a very beautiful stone, regarded as the purest form of chalcedony and assessed by some collectors as more attractive than the agate. Very often it has a flesh tint, but the colour can range from yellow, through brown to red. The red variety is often confused with jasper (which we shall discuss later) by people who are unaware that jasper is completely opaque and carnelian is translucent. If you hold up a pebble of reddish carnelian to a strong light, even though it is very beach-worn and coated, you will see a delightful, roseate glow within it. Pebbles that have red speckles are not carnelian but an impure kind of chalcedony. Good specimens of carnelian must be of uniform colour and wholly translucent. The deep, clear red variety responds best of all to the lapidary’s skill. It was highly esteemed in ancient Rome and must have been still much in favour in the eleventh century, for, to quote Marbodus again:
Let not the Muse the dull cornelian slight Although it shine with but a feeble light; Fate has with virtues great its nature graced. Tied round the neck or on the finger placed, Its friendly influence checks the rising fray And chases spites and quarrels far away.
The pebbles are found on some beaches on the east coast of Scotland, and on the coasts of Cornwall, the Isle of Wight, Kent, especially near Deal, Yorkshire and Suffolk. The Felixstowe and Cromer beaches have yielded many good specimens.
In your search for carnelians or any other pebbles of translucent stone you should adopt a technique for ‘beach-combing’ of a more general kind. Select that strip of shingle from which the tide has very recently receded and walk very slowly along it with the sun right in front of you, keeping your eyes on the pebbles a yard or two ahead of you. If a carnelian is peeping out from among its more commonplace companions, its translucent quality will be just sufficient to draw your gaze towards it. But, you may object, one cannot order the movements of the sun to coincide with one’s visits to the beach in such a way as to ensure this method of search. Obviously not. Everything depends on the orientation of the beach and the time of the visit. But, given all the favourable conditions, you can take advantage of them.
Commercial carnelian does not always live up to its description. The fleshy redness of the natural carnelian is due to the presence of iron oxide in the stone. It can be artificially created by staining or by treating the stone with a solution of one of the salts of iron and then heating it.
The last of the translucent members of the quartz family that calls for notice here is Sard. It is really a variety of carnelian, but it is harder, tougher, of richer colour, of more uniform quality and of brighter lustre than ordinary carnelian. Hence it is more valuable. Sard of the choicest kind is said to possess the rare quality of chatoyance. This word (derived from the French: chat = cat) means the changing of colour in the lustre as the stone is moved around in the light. The similar behaviour of cats’ eyes in the darkness doubtless gave rise to the term. The peculiar toughness of sard also enhances the value of the stone. Very ancient specimens retain a smooth and bright surface long after harder and more precious gems show signs of wear.
You will be fortunate indeed to find one, but, having found one, you will find it hard to distinguish it from carnelian, as the two stones are of the same chemical composition—that is, chalcedony coloured by iron oxide—and they shade off, one into the other. It is impossible to draw precisely a border-line between the two.
Before we leave the subject of chalcedonic quartz pebbles we must refer to one more variety, not because you are ever likely to discover one, but because its name is a compound of two that we have already considered and may consequently be confusing to you unless its nature is now made clear. This is the Sardonyx. It is by far the most valuable member of the chalcedony family. It probably acquired this name because it is a fusion of certain qualities of the sard and the onyx. In its straight, parallel banding it is an onyx, but one or more of the bands consist of sard or carnelian. The bands are white and either brown or red. Exquisite specimens come from India and Arabia to be cut into seals and cameos. There has always been a brisk trade in imitation sardonyx, produced by the chemical treatment of cheap Brazilian agate or inferior carnelian. Only an expert gemmologist can detect the difference between the genuine and the imitation stone.
And now for a look at Jasper, an opaque variety of quartz. It is very much commoner on the beaches than its translucent relatives and is almost valueless, being an inferior form of quartz, but it has a charm of its own to the pebble-collector. He appreciates it for its colour and its hardness. The colour is usually a dull red, but it is sometimes brown or yellowish-green. One or other of the salts of iron is responsible for the colouring. If you break a pebble of jasper, the fresh fracture will reveal through your pocket lens a multitude of tiny quartz grains mingled with material that looks like dried clay. In fact, it is clay. But for its presence the pebble would consist of pure quartz. The admixture of the clay has made it impure and completely opaque. The point of your knife will make a faint mark on the surface of the jasper pebble and, as you know, would make no impression upon it if it were quartz.
You should not dismiss the jasper with contempt because of its impurity and opaqueness. The pohshed pebble will look well in your collection. If you chance to find a pebble of conglomerate in which fragments of jasper are intermingled with those of quartz, snatch it eagerly. A pohshed shoe of it would grace your cabinet, for it resembles a superlative piece of inlaid work.
Jasper pebbles are to be found on so many of our beaches that a list of localities would be superfluous. On some Yorkshire and Devonshire beaches you may find some very pleasingly striped varieties. These are stones that he midway between the jasper and the agate. They provide a reminder to us that all the varieties of quartz have no clear fines of demarcation. They tend to merge one into another. The Bloodstone, sometimes called the Heliotrope, is another variety of jasper and is much less frequently encountered than the ordinary red jasper pebble. Its colouring is a rich green, mottled with blood-red spots. This vividly contrasting combination gives it a singular beauty, which becomes resplendent when the stone is cut and polished. Good specimens are a little less opaque than ordinary jasper and this slight translucency enhances their charm. The word ‘heliotrope’ suggests to us the purple tint of the flowers called by that name, but it applied originally to certain tropical flowers that turned with the sun, being derived from the Greek words meaning ‘sun’ and T turn’. It must have been given to the stone because of the popular belief that the image of the sun turned to the colour of blood when one looked at its reflection in the stone.
Here we must leave quartz and all its relatives that together comprise the fascinating silica family. In parting from them we must take the risk of becoming wearisome and offer a few words of advice to those who are eager to seek them on the beach.
Firstly, bear always in mind that pebbles of these lovely stones do not reveal themselves to the casual beach wanderer, for, like all other beach pebbles, they have endured the rolling of the tides, the bleaching of sun and wind and the coating that all pebbles acquire in course of time. At first you will experience disappointment even on the beaches reputed to have a high content of the semi-precious varieties of silica; but on the second, or perhaps the third, day of patient searching, you will suddenly become aware with a delicious thrill that you have gained the knack of piercing the disguises of the chalcedonic pebbles. Thenceforward your progress will be rapid and joyous.
Secondly, the beaches specifically mentioned in the foregoing paragraphs as being well stocked with these pebbles are not the only parts of the coast which could reward your search for them. Not many beds of shingle are completely devoid of them. The least promising beaches are those in deep bays guarded by long headlands, which set up a formidable barrier against longshore drifting. But even here your search will not be in vain if the cliffs at the back of the beach are of igneous or metamorphic rocks or if they are surmounted by a layer of boulder clay. The unproductive beach is the closely guarded one on a coast backed by cliffs of limestone or shale.
Thirdly, the modern nomenclature of the semi-precious stones differs, in some respects, from the old and can cause some bewilderment to those who are unaware of the changes. The peoples of old used the names of their ornamental stones rather loosely, so, if you come upon a passage in biblical or classical literature referring to a stone in terms contradictory to those used in this article, do not begin to wonder whether you have been misled. Here, for instance, is a reference to jasper, which we know to be opaque: ‘And her light was like unto a stone most precious, even like a jasper stone, clear as crystal.’ (Revelation, xxi, 11.) Obviously, the jasper was the name of one of the precious and completely transparent stones at the time when those words were written.
Now we must look at two stones that have originated from the vegetable kingdom. Their distribution on our coast is somewhat local, but they are of sufficient interest, value and appearance to merit some attention. They are Jet and Amber.
Jet is a very close relative of coal, especially of lignite (wood-coal), bituminous coal and anthracite, but it is much harder and glossier and possesses the qualities that entitle it to rank as an ornamental stone. A thin slice of it shows that it has a woody texture and it might be designated as wood, decomposed, fossilized or bituminized, yet all the softness of the woody fibres has gone and, like any other stone, jet sinks in water.
A polished pebble of good-quality jet is of midnight black with a brilliant lustre, caressingly smooth to the touch, of light weight and entirely opaque. Inferior jet is black with a tinge of brown and is a little softer. The only substantial deposits of jet in Great Britain are at Whitby on the Yorkshire coast, in that same formation of shale as occur the ammonites or snake-stones. It is strange that no jet is found in other parts of the country where shale abounds and where huge accumulations of the decomposed wood of ancient forests have caused the formation of coal-seams.
The biggest mass of it occurs in a cliff appropriately named the Jet Rock. The layer runs inland for a considerable distance. Long ago the task of the jet-workers was easy. They had only to roam the beach and pick up lumps of it. These lumps were parts of the residue of cliffs broken down by the attacking waves. When that supply became exhausted, the jet-workers had to drive galleries into the cliffs and sink shafts inland. Meanwhile the longshore drifting, which, on this coast, as you should remember, is from north to south, carried many of the jet pebbles down the east coast. Some of them are still picked up many miles south of Whitby.
Jet began to be fashionable in the Bronze Age. The burrows or graves of that prehistoric era have yielded bracelets, rings, beads, necklaces and other ornaments of jet. Roman literature contains references to the bountiful supply of jet in Britain and numerous ornaments carved from it have been excavated from the sites of villas and garrison towns inhabited by the Romans during their long occupation of this country. The source of all of them was probably Whitby, where the jet-workers can surely boast of being engaged in one of the oldest, if not the very oldest, trade in Great Britain. Whitby jet was high in the list of British exports to the Continent in the Middle Ages. We have since imported jet from Spain and France, but it is softer and less glossy than the Whitby product. There are numerous imitations, including Pennsylvania anthracite, bituminous coal, black glass, black obsidian and chalcedony stained black. The feminine demand for jet ornaments fluctuates. They were much in vogue with our grandmothers and great-grandmothers, who delighted in jet necklaces and fringes adorned with jet beads.
If you find on the east coast a pebble that you think is jet, you can easily make sure of it. Scrape the surface to reveal the dense blackness, hardness and glossiness. Test its weight. It should be very light. If it is not lighter than a piece of glass of the same size, it is not jet. To make quite sure, break off a piece and hold it in the flame of a match. It should burn with a greenish flame and give off a pleasant smell, sweet and suggestive of tar. There is supposed to be another test, which, so far, the author has not had the courage to apply, alluring though it is. Pour oil on the burning jet and it will quench the flame, but pour water on it and you will have a crackling conflagration.
Occasionally and erroneously jet is called black amber, because it possesses, though only to a slight extent, the property of becoming electrified by vigorous rubbing and of attracting small objects as a magnet attracts iron filings.
And this leads us to the second of our two stones of vegetable origin, Amber, known to the ancient world as electron, from which we get our word electricity. Most schoolboys have seen their science master rub a piece of amber on cloth and then hold it over a pile of little scraps of paper, whereupon the scraps fly up to the amber and cling to it.
Strictly speaking, amber is not a stone. It consists of fossil resin. In the remote past the liquid resin bubbled out of pine-trees, now long extinct, in forests of vast extent, stretching from the Baltic to the Mediterranean. The hardened fossilized resin was washed by the waves out into the Baltic Sea, the biggest deposits being off the coast of Pomerania. When the liquid amber exuded from the trees and dropped on the ground it gathered up a motley collection of fragments and slowly solidified around them. It entombed within itself gnats, flies, spiders and beetles and numerous little creatures that then inhabited the trunks of pine trees. Their fossilized remains, clearly visible in the amber, present an enthralling study to entomologists, especially because they are unlike the insects now inhabiting northern Europe and resemble those that now exist in more southern, and therefore warmer, latitudes.
The deposits of amber in the Baltic were rolled along, as the centuries passed, into the North Sea and by infinitely slow stages to our east coast. Pieces of it are still being picked up on the beaches between Yorkshire and Essex, especially at Cromer, Yarmouth, Southwold, Aldeburgh and Felixstowe. If you are fortunate enough to find one, you can quickly make up your mind about it. The colour varies from pale primrose to deep orange. It is the softest of all the stones we have mentioned, being only a little harder than rock-salt, which can be scratched with the finger-nail, and a knife-blade will therefore make a deep impression in amber. It is also brittle and, like jet, is fight in weight and burns in a match flame. The colour of the flame is yellow and the odour it emits is aromatic. Of course, the most convincing of tests is to tear up a small sheet of paper into pieces, rub the amber on your sleeve and watch its effect upon the pieces of paper when you hold it above them. Do not expect to find any pieces larger than a small nut. One extremely lucky person found on the Suffolk coast, over a hundred years ago, a large block of it weighing thirteen pounds and of an estimated value of £4,500. We hesitate to suggest what sum a block of that size would command in the currency of to-day, but you should think twice before rushing to Suffolk in the hope of finding a replica of it and of thus ensuring an immediate and comfortable retirement.
For personal ornamentation amber has been in demand in Europe since the late Stone Age. We know that amber ornaments were in vogue in Britain in the Bronze Age, because they have been found here in tombs of that period, but it is in the East that amber has been most highly prized. Great quantities have been exported from the German shores of the Baltic to Constantinople, Egypt, Arabia, India and Persia, there to be fashioned into ornaments of all descriptions. It was, and still is, frequently carved into mouthpieces for pipes. The hookah-smokers of Turkey regarded it almost with veneration, for in that country it was thought to be a complete safeguard against infection. As it was the courteous custom to offer a guest in a Turkish household a pull at the family hookah, he could enjoy his smoke without fear of inhaling any of the bacilli that his hosts might have been entertaining unawares.
It is time now to leave the semi-precious stones and to visit the workshop of the lapidary to see how he does the cutting and polishing to which we have made such frequent reference. These processes, especially when applied to the very hard stones such as chalcedony and its varieties, are long and arduous, so you should select only the very best of your specimens for his attention. Pebbles of the less refractory kind are cut fairly easily and, consequently, less expensively.
The cutting and the polishing of gems have been going on for over 4,500 years. Egyptian lapidaries were cutting scarab seals and those of Assyria and Babylonia cylindrical seals at least as early as 2500 B.C. They did it by hand or with the most primitive of instruments. The story of the developments, and also the setbacks, in the art through the thousands of subsequent years is very engaging, but this is not the place for its narration. We must enter the workshop of the twentieth-century lapidary. In London he will be found at work in the Hatton Garden district, the centre of the jewellery and gem-cutting trades. If you live in London and take your pebbles home for treatment, you must make your way there, but you may find the lapidaries too busily engaged in gem-cutting to bother about your pebbles. If you cannot wait for the end of your holiday and happen to be spending it at one of the larger seaside resorts which have beaches that yield interesting pebbles, the local lapidary’s shop, usually near the beach, invites your custom. You may be sure that he is familiar with that beach and you should certainly take his advice upon the choice of your stones for cutting. Occasionally he is to be found at the smaller seaside places, where the shingle is unusually rich in attractive pebbles: the Cornish coast, for instance, which is an El Dorado for the pebble-collector.
Having entered, you will want to stay, not only to see the fascinating operations he performs on the pebbles, but also to gaze at the fashioned stones awaiting delivery. In both the processes of cutting and polishing the hard pebbles of semi-precious stone, the lapidary works with discs. For cutting he uses the rim of a steel disc; for polishing he uses the flat surface of another disc. In other words, the first wheel or disc cuts by its edge, the second polishes by its surface.
All but the very hard stones are cut with comparative ease with saws of tempered steel. Granite, for instance, is dealt with in this way. The expression ‘hard as granite’ must have been put into circulation by a person who knew nothing of mineralogy, for, though granite seems hard to the touch, it is soft in comparison with flint, jasper and the varieties of chalcedonic quartz. To cut them the lapidary uses a disc of soft steel. Why a soft disc for such hard stones? Well, a pebble of agate or jasper would quickly wear out the teeth of the most highly tempered saw, but it will not easily wear out a steel rim soft enough to have dia- mond dust embedded in it. Diamond stands at the top of the hardness scale for minerals.1 Mixed with oil into a paste it is rubbed into the rim of the soft steel wheel, which has first been scarified by the lapidary’s knife. The diamond dust lodges in the scratches and enormously reinforces the steel rim of the electrically driven wheel. Indeed, it imparts to the rim an adamantine hardness, for diamond is adamant—that is, a stone of impenetrable hardness.
After the pebble has been cut in two, you or the lapidary (preferably the latter) must decide whether either of the cut surfaces is worthy of being polished. There will be some little difference between them, because a section as thick as the disc has been cut out from between them. Before the polishing process begins it may be necessary to remove some little scars or notches which the cutting operation has left on the surface. The lapidary grinds the surface down to completely even flatness by pressing the pebble down on a disc of lead or copper, having first spread on the disc a paste of fine grains of emery. Emery is a variety of carborundum, which comes next in the scale of hardness to the diamond. The grains become embedded in the rotating wheel and quickly remove the irregularities. Polishing then begins. It usually consists of two operations. The first one is conducted on a wooden disc (sometimes on one of leather) on which powdered pumice stone has been scattered. The final one, which imparts the high, gleaming polish, is done on a wheel made of felt, the polishing medium being rotten stone, otherwise called tripolite or tripoli powder, a sandy, friable earth of a greyish-white colour. Sometimes the lapidary employs a chemical preparation for this final polish. If the interior of your pebble has fulfilled your expectations, whether in richness of colour, delicacy or intricacy of pattern or-attractiveness of its fossilized contents, you will be delighted with the lustrous sheen that the lapidary’s polishing has given to it.
Do not forget to take back with you the other half of your pebble to take its place in your collection as the fellow of the polished piece. The latter you will display, of course, with its polished surface uppermost; the former with its cut surface downwards. It is most desirable to show the polished surface in juxtaposition with the rough, weathered surface of the same stone, not only to provide a striking contrast, but to help you to keep in mind what a pebble of this particular kind looks like on the beach. You will be pleasantly surprised to find how greatly this will facilitate your future searches among the shingle.
Some fervent pebble-collectors, gifted with mechanical knowledge, unlimited patience and manual dexterity, set up their own workshops and spend gratifying winter evenings in fashioning the pebbles they have hoarded in the summer. Lacking all these enviable qualities, we have not ventured to follow their enterprising example and we counsel you to be equally unresourceful, unless, of course, you are a mechanical genius. The usual rewards of the amateur lapidary are lacerated fingers, splinters of stone in the eyes, mutilated pebbles and a wasteful expenditure of diamond dust.
If you fail to secure the services of a lapidary, or if you cannot go to the trouble of finding one, you may perhaps find some satisfaction in the following cheap and easy method of giving your pebbles a polished appearance.
Just as a clean, wet pebble displays a clearer surface than a dry one, so a clean, varnished pebble reveals a surface at least as clear and retains it for a much longer period. While the sheen of the varnish lasts, the pebble almost appears to have been polished. You can also apply the varnish to a flattened side of a pebble. All limestones, for example, and many other rocks that are not high on the scale of hardness, rub down easily on a flat piece of tough sandstone or grit. A smoother polish may be obtained on a flat piece of carborundum, and a still better one by using different grades of carborundum powder on a piece of plate glass.